Tooth enamel, along with dentin, cementum, and dental pulp (see FIG. 1) is one of the four major tissues that make up the tooth. It is the hardest and most highly mineralized substance in the human body. Ninety-six percent of enamel consists of mineral, with water and organic material composing the rest. The primary mineral is hydroxyapatite, which is a crystalline calcium phosphate.
The high mineral content of enamel, which makes this tissue the hardest in the human body, also makes it susceptible to a demineralization process which often occurs as dental caries, otherwise known as cavities. Demineralization occurs for several reasons, but the most important cause of tooth decay is the ingestion of fermentable carbohydrates.
Tooth cavities occur when acids dissolve tooth enamel:Ca10(PO4)6(OH)2(s)+8H+(aq)→10Ca2+(aq)+6HPO42−(aq)+2H2O(1)
Sugars from candies, soft drinks, and even fruit juices play a significant role in tooth decay, and consequently in enamel destruction. The mouth contains a great number and variety of bacteria, and when sucrose, the most common of sugars, coats the surface of the mouth, some intraoral bacteria interact with it and form lactic acid, which decreases the pH in the mouth. Then, the hydroxylapatite crystals of enamel demineralize, allowing for greater bacterial invasion deeper into the tooth. Demineralization involves the loss of calcium, phosphate, and carbonate. These cycles of demineralization and remineralization continue throughout the lifetime of the tooth.
Fluoride works to control early dental caries in several ways. Fluoride concentrated in plaque and saliva inhibits the demineralization of sound enamel and enhances the remineralization (i.e., recovery) of demineralized enamel. As cariogenic bacteria metabolize carbohydrates and produce acid, fluoride is released from dental plaque in response to lowered pH at the tooth-plaque interface. The released fluoride and the fluoride present in saliva are then taken up, along with calcium and phosphate, by demineralized enamel to establish an improved enamel crystal structure (FIG. 2). This improved structure is more acid resistant and contains more fluoride and less carbonate. Fluoride is more readily taken up by demineralized enamel than by sound enamel.
Fluoride also inhibits dental caries by affecting the activity of cariogenic bacteria. As fluoride concentrates in dental plaque, it inhibits the process by which cariogenic bacteria metabolize carbohydrates to produce acid and affects bacterial production of adhesive polysaccharides (FIG. 3).
The scientific support for remineralization by fluoride is well established. Wu (2012), for example, used enamel specimens in an in vivo model of demineralization and remineralization wherein specimens were observed by stereomicroscope and scanning electron microscope and compared in surface microhardness value. These workers found a distinct difference in micro-morphologic appearance on fluoride enamel surface. Artificial caries of fluoride enamel showed a relatively complete surface, the surface microhardness after demineralization and remineralization in fluoride group was higher than non-fluoride group (P<0.05). They concluded that fluorinated enamel can enhance cariostatic potential and remineralization capacity of dental enamel.
Similarly, Austina (2010) investigated the effect of an aqueous sodium fluoride solution of increasing concentration on erosion and attrition of enamel and dentine in vitro. Enamel and dentine sections from caries-free human third molars were polished flat and taped (exposing a 3 mm×3 mm area). All specimens were subjected to 5, 10 and 15 cycles of experimental wear with artificial saliva, erosion and attrition. Following tape removal, step height (SH) in μm was measured using optical profilometry. These scientists found that 5000 ppm and 19,000 ppm sodium fluoride solutions had a protective effect on erosive and attritional enamel tooth wear in vitro, however no other groups showed significant differences. They concluded that the more intensive the fluoride regime, the more protection was afforded to enamel from attrition and erosion. However, no such protective effect was demonstrated for dentine.
Thus, the evidence fully supports the value of applying fluoride gel or other product containing a high concentration of fluoride to the teeth to leave a temporary layer of calcium fluoride-like material on the enamel surface.
Of course, too much fluoride can be harmful as well, especially in younger children whose teeth are still developing. A NCHS Data Brief No. 53 published in 2010 established that while tooth decay decreases with fluoridating water, fluorosis increases, especially in children. Dental fluorosis is defined as a change in the mineralization of the dental hard tissues (enamel, dentin, and cementum) caused by long-term ingestion (eating and drinking) of fluoride during the period of tooth development prior to eruption into the mouth (first 8 years of life for most permanent teeth excluding third molars). Once the tooth erupts, dental fluorosis refers to a range of visually detectable changes in enamel. Changes range from barely visible lacy white markings in milder cases to converged opaque areas and pitting of the teeth in severe forms. After eruption the pitted areas can become stained yellow to dark brown.
Fluoride containing gels and rinses are available for use in managing dental health, but nothing specifically developed for orthodontic use has yet been developed.
OrthoAccel has developed a revolutionary orthodontic treatment device that can be used in conjunction with e.g., braces, retainers, positioners, fixed class II correctors and clear positioners. US2008227046 et seq, and US20120322018 describe a vibrating device that can reduce orthodontic treatment time by as much as 30-50%. This device, known as AcceleDent®, includes a detachable bite plate allowing for contact with occlusal and facial and/or lingual teeth (maxillary and mandibular). The bite plate is reversibly coupled to an extraoral housing containing a rechargeable battery coupled to a vibrator coupled to a processor that can record and transmit device usage or compliance data.
In additional to cyclic forces (aka microvibration), OrthoAccel is experimenting with other treatment modalities that can further speed orthodontic remodeling, including low energy IR laser dental devices (61/624,242, filed Apr. 13, 2012) and electric micropulse based devices (61/673,236, filed Jul. 18, 2012). Each of these new devices can be made with the same or similar detachable bite plates provided with the AcceleDent® device.
Demineralization is a particular problem that often accompanies orthodontic treatment. People with orthodontic braces often have trouble properly brushing their teeth due to brace bulk and the result is a build-up of plaque near the braces. The acids in plaque can severely harm tooth enamel and eventually cause cavities, but the first evidence of this type of tooth decay is the white decalcified enamel spot or lesion that suddenly becomes apparent when braces are removed.
It would thus be particularly beneficial if the AcceleDent® could provide the user with fluoride during use, thus helping to avoid the demineralization that often occurs with brace usage. Of course, any of the existing fluoride gels or foams could be applied to the bite plate before use, but such liquids tend to be messy, thus discouraging their use. Instead, a device that releases fluoride only in a wet oral environment would eliminate both the mess and the need to apply gel. Further, since the device is only indicated for 20 minutes usage a day, it also addresses the concerns over excess fluoride, and presents less significant FDA hurdles in approval.
Thus, what is needed in the art is a bite plate, designed for orthodontic use, that steadily releases beneficial fluoride ions during use.